3GPP (3rd Generation Partnership Project) is a project to discuss/create specifications of a mobile telephone system based on networks of evolved W-CDMA (Wideband-Code Division Multiple Access) and GSM (Global System for Mobile Communications). In 3GPP, the W-CDMA system has been standardized as the third generation cellular mobile communication system and its services have been launched sequentially. Further, HSDPA (High-Speed Downlink Packet Access) with the communication speed further increased has also been standardized and its services are launched. In 3GPP, the evolution of the third generation radio access technology (hereinafter, referred to as “EUTRA (Evolved Universal Terrestrial Radio Access)” is discussed.
As a downlink communication system in EUTRA, there is proposed an OFDMA (Orthogonal Frequency Division Multiple Access) system in which user multiplexing is performed using subcarriers orthogonal to each other. Further, in the OFDMA system, such a technology has been applied as an adaptive modulation and coding scheme (AMCS) based on adaptive radio link control (Link Adaptation) such as channel coding. AMCS is a scheme, in order to efficiently transmit high-speed packet data, for switching radio transmission parameters (hereinafter, referred to as AMC mode), such as an error correction scheme, coding rate of error correction, and data modulation order, in accordance with the channel quality of each mobile station apparatus. The channel quality of each mobile station apparatus is fed back to the base station apparatus using CQI (Channel Quality Indicator).
In OFDMA, a communicable region can be divided physically into a frequency domain corresponding to subcarriers and a time domain. The several divided regions combined to one unit is called a physical resource block and one or more physical resource blocks are allocated to each mobile station apparatus and communication is established in which a plurality of mobile station apparatuses is multiplexed. In order for the base station apparatus and each mobile station apparatus to establish communication of optimum quality and at speed in accordance with the request, it is necessary to determine allocation to a physical resource block and a transmission scheme in consideration of the channel quality of a frequency band corresponding to each subcarrier in each mobile station apparatus. The determination of the transmission scheme and scheduling are made by the base station apparatus, and therefore, the channel quality for each frequency domain is fed back from each mobile station apparatus to the base station apparatus in order to realize the request. Further, when necessary, information indicative of a frequency domain (for example, one having good channel quality) selected by each mobile station apparatus is fed back to the base station apparatus.
In EUTRA, in order to increase the communication path capacity, the utilization of transmission diversity has been proposed, such as SDM (Space Division Multiplexing) that utilizes MIMO (Multiple Input Multiple Output), SFBC (Space-Frequency Block Coding), or CDD (Cycle Delay Diversity). MIMO is a general term for a multiple-input/multiple-output system or technique and characterized by transmitting using a plurality of antennas on the reception and transmission sides and by setting the number of branches of input/output of radio waves to two or more. The unit of signal sequence that can be transmitted with space division multiplexing by utilizing the MIMO scheme is called a stream. The number of streams (Rank) at the time of the MIMO communication is determined by the base station apparatus in consideration of the channel status. The number of streams (Rank) required by the mobile station apparatus is fed back from the mobile station apparatus to the base station apparatus using RI (Rank Indicator).
When SDM is used in the downlink, preprocessing of the transmission signal sequence in advance (this is called “precoding”) has been examined in order to accurately separate information of a plurality of streams transmitted from each antenna. The information of precoding can be calculated based on a channel status estimated by the mobile station apparatus and is fed back from the mobile station apparatus to the base station apparatus using PMI (Precoding Matrix Indicator).
As described above, in order to realize communication with optimum quality, it is required to feed back various pieces of information indicative of a channel status from each mobile station apparatus to the base station apparatus. This channel feedback report (channel status information) is formed by the CQI, PMI, RI, etc. The number of bits and the format of the channel feedback report are specified to the mobile station apparatus by the base station apparatus in accordance with the circumstances.
FIG. 17 is a diagram showing a channel configuration in EUTRA (refer to Non-patent Document 1). Downlink in EUTRA includes a physical broadcast channel (PBCH), a physical downlink control channel (PDCCH), a physical downlink shared channel (PDSCH), a physical multicast channel (PMCH), a physical control format indicator channel (PCFICH), and a physical hybrid ARQ indicator channel (PHICH). Further, Uplink in EUTRA includes a physical uplink shared channel (PUSCH), a physical random access channel (PRACH), and a physical uplink control channel (PUCCH).
In EUTRA, it is not possible for the mobile station apparatus to perform simultaneous transmission using different channels (for example, the PUSCH and the PUCCH) because of the properties of the uplink single carrier. When performing transmission using these channels at the same timing, it is required for the mobile station apparatus to multiplex information in accordance with the definition of the specifications and then transmit the information using a determined channel or to transmit only one piece of information in accordance with the definition of the specifications etc. (other pieces of data are not transmitted (dropped)).
The PUCCH is a channel used to transmit the channel feedback report (CQI, PMI, RI), a scheduling request (SR) for the mobile station apparatus to request for allocation of resources to transmit uplink data (request for transmission of UL-SCH), and uplink control data, such as HARQ ACK/NACK for the downlink transmission.
On the other hand, the PUSCH is mainly used to transmit the uplink data, however, when the data is not transmitted using the PUCCH, the channel feedback report is also transmitted together with the uplink data (UL-SCH) using the PUSCH. That is, the channel feedback report is fed back to the base station apparatus using the PUSCH and/or the PUCCH as a result. In general, in one subframe, the size of a resource to be allocated to transmit the channel feedback report is larger in the PUSCH than in the PUCCH and it is possible to transmit a more detailed channel feedback report (information of about 20 to 100 bits or more when the number of physical resource blocks supported by the base station apparatus and the mobile station apparatus is 65 to 110 (20 MHz system bandwidth). It is only possible for the mobile station apparatus to transmit information about 15 bits or less in one subframe using the PUCCH.
It is possible for the mobile station apparatus to periodically transmit the channel feedback report using the PUCCH. Further, it is also possible for the mobile station apparatus to transmit the channel feedback report using the PUSCH periodically or a-periodically (Non-patent Documents 1 and 2). For example, it is possible for the base station apparatus to permit the mobile station apparatus to periodically transmit, using the PUSCH, the channel feedback report by setting a continuous (persistent) resources of the PUSCH and the period (or period and offset) to transmit the channel feedback report using a RRC signaling (radio resource control signal).
Further, it is also possible for the base station apparatus to permit the mobile station apparatus to periodically transmit, using the PUSCH, the channel feedback report by setting the period (or period and offset) to transmit the channel feedback report using the RRC signaling (radio resource control signal) and transmitting an uplink transmission permission signal (referred to as an uplink grant, L1/L2 grant, scheduling grant, etc., however referred to as an uplink transmission permission signal hereinafter) to initiate transmission of the channel feedback report (to activate the channel feedback report) using the PDCCH. In the case of a periodic channel feedback report, in ordinary cases (except for the case where the uplink transmission permission signal overwrites the periodic channel feedback report etc.), the mobile station apparatus does not transmit the uplink data and the channel feedback report at the same time but transmits only the channel feedback report to the base station apparatus using the PUSCH.
Furthermore, it is possible for the base station apparatus to permit the mobile station apparatus to a-periodically (temporarily, one-shot) transmit, using the PUSCH, the channel feedback report and the uplink data by including one-bit information (channel feedback report request or channel status report trigger) to make a request for the transmission of the channel feedback report in the uplink transmission permission signal. It is also possible for the mobile station apparatus to a-periodically transmit, using the PUSCH, only the channel feedback report. Transmission of only the channel feedback report means that the mobile station apparatus does not transmit the uplink data and the channel feedback report at the same time but transmits only the channel feedback report to the base station apparatus.
In EUTRA, FIG. 18 is a diagram illustrating an example of multiplexing when the mobile station apparatus transmits the uplink data (shown by a lattice pattern), the channel feedback report (shown pale solid black), and ACK/NACK (shown by a mesh pattern) at the same time using the PUSCH. In FIG. 18, in addition to the uplink data, the channel feedback report, and the ACK/NACK, an uplink reference signal (hereinafter, referred to as “RS (Reference Symbol)”) used when the mobile station apparatus decodes the information is also illustrated. The RS is shown by a dotted pattern in FIG. 18.
When the mobile station apparatus multiplexes the uplink data, the channel feedback report, and the ACK/NACK, first, the channel feedback report is mapped in the time axis direction. FIG. 18 illustrates that the channel feedback report is mapped first in the time axis direction and after the channel feedback report is mapped in all the regions in the time axis direction (in this example, after the channel feedback report is mapped in the 12 regions except for the RS), the channel feedback report is mapped in the frequency axis direction (time first mapping). Here, the number of regions in which the channel feedback report is mapped differs depending on the MCS (Modulation and Coding Scheme, modulation scheme, and/or coding scheme) of the channel feedback report (the modulation scheme and/or the coding scheme may be fixed to default values).
Subsequently, like the channel feedback report, the uplink data is also mapped in the time axis direction first, and then, mapped in the frequency axis direction (time first mapping). The channel feedback report is mapped at the front (beginning) of the uplink data. After the channel feedback report and the uplink data are mapped with a time first mapping, the ACK/NACK is mapped adjacent to the RS as shown in FIG. 18. At this time, the ACK/NACK is mapped by overwriting the uplink data (this is described as follows: the ACK/NACK is mapped by puncturing the uplink data). The number of regions in which the ACK/NACK can be mapped is four at the most (in the figure, the four regions adjacent to the RS, that is, the third, fifth, tenth and twelfth regions from the smaller values along the time axis of the 14 regions in the time axis direction). The mobile station apparatus transmits the uplink data, the channel feedback report, and the ACK/NACK multiplexed as described above to the base station apparatus at the same time using the PUSCH.    Non-patent Document 1: 3GPP TS (Technical Specification) 36.211, V8.2.0 (2008-03), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channel and Modulation (Release 8)    Non-patent Document 2: “Uplink Control Signaling with Persistent Scheduling”, 3GPP TSG RAN WG1 Meeting #52, R1-080739, February 2008    Non-patent Document 3: “Two-layer CQI Scheme for Improved PUCCH Efficiency”, 3GPP TSG RAN WG1 Meeting #49bis, R1-073009, June 2007